1. Technical Field
The present invention relates to an apparatus and method for printing on a web of material and more particularly to an improvement for printing on the material as the material is advanced relative to a printhead.
2. Description of the Prior Art
A conventional printer requires that a material be advanced in close proximity past a printhead that then prints markings upon that material. Such known printinq systems can use a rotating roller platen in conjunction with driven feed rollers. The roller platen provides a firm surface to maintain the material in a close relationship with the printhead and the driven feed rollers advancing the material past the head. Such systems are generally used in cash registers, label printers and computer output devices.
In such printing systems, it is often desirable to provide an enlarged opening between the printhead and the roller platen to allow free movement of the material when the system is not printing. In the prior art, the enlarged opening was created by moving either the roller platen or the printing head away from the other as illustrated by U.S. Pat. No. 4,617,577 issued Oct. 14, 1986 to Takahashi et al.
Other known art provides an area with diminished radius on the roller platen so that when the area of diminished radius is adjacent to the printhead, the opening is enlarged as illustrated by U.S. Pat. No. 4,556,333 issued Dec. 3, 1985 to Stefansson. In the Stefansson patent the roller is used as an inking drum and operates with a second inked roller to apply ink to a sheet of material. Accordingly, there is no separate ink ribbon since the ink is applied from the surface of the roller platen.
The embodiments in which an enlarged opening is created advance the material past the printhead through the use of driven feed rollers or spools on which the material is wound. A forward roller or spool draws the material past the printing head and a rear roller or spool provides tensioning to prevent slack buildup either by a driving mechanism or other means such as a friction brake.
The mechanisms for advancing the material are necessarily complex since the speeds of the driven feed rollers or spools must be perfectly coordinated with the speed of the roller platen to prevent jamming or smudging of the material due to improper feed rates. Such mechanism is expensive and complex to build and subject to wear and misadjustment which reduce the effectiveness of the printer.
Accordingly, the object of the present invention is to provide an apparatus and method for improved feeding of a web of material within a printer and more particularly, an apparatus and method which combine a simplified means for feeding the material with reduced possibility of that material jamming or smudging along its feed path.